WASHINGTON -- Elena Delle Donne found her shooting touch just in time to help the Chicago Sky pull away Sunday.
The rookie scored 22 points as the Sky beat Washington 93-79 to prevent the Mystics from clinching a playoff spot.
"I was missing all my open shots," said Delle Donne, who went only 6 of 18 from the floor but hit some crucial, difficult jumpers late. "I guess it was better when I was contested."
Epiphanny Prince added 21 points for the Sky (22-9), who have already clinched the Eastern Conference's top playoff spot and finished the five-game season series with four victories over the Mystics.
Swin Cash had 16 points and Sylvia Fowles had 13 points and nine rebounds to help Chicago won its seventh game in its last eight.
Ivory Latta scored 18 points on six 3-pointers for Washington (14-17), which closed within two points in the third quarter but never led after the first. The Mystics have lost two straight.
"No rotations, defensive breakdowns, lack of communication," Latta said after the Mystics were outrebounded 37-26 and saw the Sky hit 24 of 28 foul shots. "That explains the whole game."
Crystal Langhorne added 16 points for the Mystics, who can still clinch their first playoff berth in three seasons with a win or a loss by New York. Washington visits Indiana on Tuesday night, while New York hosts Phoenix.
Down 63-58 at the end of the third, Washington closed within three on Kia Vaughn's inside basket to open the fourth.
But Chicago responded with a 12-2 game-sealing run sparked in part by Prince's drawn charge on Tierra Ruffin's layup attempt.
Delle Donne hit two fading jumpers in the spurt and a free throw after a technical foul was assessed to Latta. Delle Donne's latter jumper, off the dribble from the baseline, made it 75-62 to cap the run.
"Time was running down (on the shot clock)," Delle Donne said. "Everyone seemed to be denied, so I just decided to elevate and shoot over."
Chicago kept building its lead. Shay Murphy's 3-pointer made it 78-64, Tamera Young's free throws stretched it to 82-66 and Prince's 3-pointer made it 85-68.
Latta and Tayler Hill's 3-pointers helped the Mystics to an 8-0 spurt close it to 85-76. But the Sky got offensive rebounds on their next two possessions and led 90-76 after Delle Donne's second 3-pointer of the game with 1:05 to play. She had missed six of her previous seven from beyond the arc.
"I never feel like (Delle Donne) misses a lot of shots, and I always feel like every shot is going in," Chicago coach Pokey Chatman said. "I'm glad she felt like she didn't make any. Maybe she'll come out more aggressive on Wednesday against Phoenix."
Delle Donne left inside the final minute to a loud ovation from a crowd that included a large contingent of supporters from the University of Delaware, the rookie's alma mater.
Monique Currie scored 13 points and Vaughn added 11 for Washington, 8-8 at home with one game left to play at the Verizon Center after two on the road.
"We just have to go out and win a game," Currie said about the playoff picture. "We want to win the rest of our games, so if we can look at it that way, just trying to finish the season with some momentum and not worry about it, I think that will take care of itself."